We present experimental verification of very wide band gaps at the visible by using a composite material consisting of an array of metallic nanowires embedded in a dielectric matrix. When the wavelength of the incident electromagnetic wave is long in such that the effective permittivity of the composite is negative, the electromagnetic waves will be reflected. At short wavelengths, the electromagnetic waves will go through the dielectric matrix. Therefore, the cutoff frequency is controlled by the average separation between metallic nanowires and their radii, allowing us to tune the band gap at will. These experimental results, in very good agreement with theoretical calculations, are at variant with many results that claim that the randomness will destroy the band gaps. In addition, the insulating nature of the composite minimizes the energy loss. Finally, it is easy and inexpensive to prepare samples. This work opens ground in the development of optical devices nanotechnology. © 2003 American Institute of Physics.